page_title: Fishing trawler
section_title: Further development
hierarchical_section_title: Fishing trawler / History / Further development
caption_attribution_description: The Royal Norwegian Navy armed trawler HNoMS Honningsvåg off Iceland.
context_page_description: A fishing trawler is a commercial fishing vessel designed to operate fishing trawls. Trawling is a method of fishing that involves actively dragging or pulling a trawl through the water behind one or more trawlers. Trawls are fishing nets that are pulled along the bottom of the sea or in midwater at a specified depth. A trawler may also operate two or more trawl nets simultaneously.
  There are many variants of trawling gear. They vary according to local traditions, bottom conditions, and how large and powerful the trawling boats are. A trawling boat can be a small open boat with only 30 horsepower or a large factory ship with 10,000 horsepower. Trawl variants include beam trawls, large-opening midwater trawls, and large bottom trawls, such as "rock hoppers" that are rigged with heavy rubber wheels that let the net crawl over rocky bottom.
context_section_description: Trawler designs adapted as the way they were powered changed from sail to coal-fired steam by World War I to diesel and turbines by the end of World War II.
  The first trawlers fished over the side, rather than over the stern. In 1947, the company Christian Salvesen, based in Leith, Scotland, refitted a surplus Algerine-class minesweeper (HMS Felicity) with refrigeration equipment and a factory ship stern ramp, to produce the first combined freezer/stern trawler in 1947.
  The first purpose built stern trawler was Fairtry built in 1953 at Aberdeen. The ship was much larger than any other trawlers then in operation and inaugurated the era of the 'super trawler'. As the ship pulled its nets over the stern, it could lift out a much greater haul of up to 60 tons. Lord Nelson followed in 1961, installed with vertical plate freezers that had been researched and built at the Torry Research Station. These ships served as a basis for the expansion of 'super trawlers' around the world in the following decades.
  Since World War II, commercial fishing vessels have been increasingly equipped with electronic aids, such as radio navigation aids and fish finders. During the Cold War, some countries fitted fishing trawlers with additional electronic gear so they could be used as spy ships to monitor the activities of other countries.
caption: Armed trawler HNoMS Honningsvåg off Iceland.
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